<?php
namespace IMooc;
class database
{
	protected  static  $db;
	private function __construct()
	{
		
	}
	static function getInstance()
	{
		if(self::$db){
			return self::$db;
		}else{
			self::$db = new self();
			return self::$db;
		}
		
	}
	function where($where)
	{
		return $this;
	}
	
	function order($order)
	{
		return $this;
	}
	
	function limit($limit)
	{
		return $this;
	}
}